The present disclosure relates to the assaying of an aromatic amino or aminosulphonic acid of the general formula ##STR1## wherein A is CO or SO.sub.2 and n equals 0, 1 or 2 in a urine, plasma or serum sample to determine the proper functioning of the pancreas.
Certain peptides which contain an amino or aminosulphonic acid group of the general formula ##STR2## wherein A and n have the significance given earlier, are used as diagnostic agents for the determination of the pancreas function. An especially suitable peptide for this purpose is N-benzoyl-L-tyrosyl-p-aminobenzoic acid of the formula ##STR3##
In principle, assays to determine pancreas function are carried out as follows:
A sufficient amount of a suitable peptide containing an amino or aminosulphonic acid group of formula I' is administered to a fasted trial person from whom any previous medicaments, especially sulphonamides, sulphonylurea compounds and pancreas enzymes, have been withdrawn. A sufficient diuresis is provided for by permitting water to be drunk. The peptide which has been administered is cleaved by the chymotrypsin produced by the pancreas, a large part of the amino or aminosulphonic acid of formula I being excreted in the urine as such or in metabolized form. In order to recover any metabolized amino or aminosulphonic acids of formula I, the urine is conveniently hydroylzed prior to the determination. Depending on the percentage amount of amino or aminosulphonic acid of formula I found in the urine sample, the function of the pancreas can be elucidated. When N-benzoyl-L-tyrosyl-p-aminobenzoic acid is used as the peptide, p-aminobenzoic acid is determined in the urine sample as the amino acid of formula I. The determination of the amino or aminosulphonic acid of formula I can, however, also be carried out using plasma or serum.
In the known determination method according to Bratton and Marshall, the amino or aminosulphonic acid of formula I present in the urine sample is diazotized and coupled to a coloring substance, which is then determined colorimetrically. Since this determination method is relatively costly, there exists a need for a simpler and less complicated determination method.